JP2936871B2 - Tunneling field effect transistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field effect transistor having a differential negative resistance characteristic.

[0002]

2. Description of the Related Art As a negative resistance element using tunneling, a resonant tunneling structure is combined with a heterojunction bipolar transistor or a field effect transistor.
Resonant tunneling bipolar transistor (Reson
ant tunneling Bipolar Tran
Such devices are known, and are expected to have superiority as functional elements such that an exclusive OR, a multi-state holding gate, a latch circuit, a NOR circuit, and the like can be constituted by a single transistor. These devices are described, for example, by Capasso et al. In Electron Devices.
s), vol. 36, pp 2065, 1989.

[0003]

SUMMARY OF THE INVENTION The electron affinity of semiconductors
Is required to add one electron to the semiconductor from infinity
Energy, and when considering a semiconductor heterojunction
Replaces the conduction band energy value with the electron affinity.
Can be obtained. Therefore, the propagation at the semiconductor heterojunction
The conduction energy discontinuity is the electronic parent of each semiconductor.
Expressed by the difference in power. In the conventional resonant tunneling effect, a tunnel barrier is formed using discontinuity of conduction band (or valence band) energy in a semiconductor heterojunction, that is, a difference in electron affinity (or valence band energy ) between constituent semiconductors. The tunnel barrier mentioned here is a half
It is installed to prevent the movement of charged particles from conductor A to semiconductor B.
Shows a barrier that has been broken. In this case, in order to increase the density of the tunnel current, it is necessary to reduce the height of the barrier or to reduce the thickness of the barrier. This at the same time leads to an increase in the density of electrons crossing the barrier due to thermal excitation, increasing the leakage current. Therefore, it was difficult to realize a large differential negative resistance at room temperature.

[0004]

According to the tunneling field effect transistor of the present invention, the inter-band tunneling between the conduction band and the valence band can be performed in comparison with the conventional in-band (in the conduction band or in the valence band) tunneling. Since it is used, a leak current can be suppressed and a large tunnel current can be obtained. From the conduction band of semiconductor A to the valence band of semiconductor B
When the tunnel phenomenon is used, a tunnel barrier layer is used.
Therefore, conduction band energy discontinuity is large for semiconductor A.
Large valence band energy discontinuity for semiconductor B
This is because it is possible to use critical materials.

[0005]

[Function] Inter-band tunneling between the conduction band and the valence band is caused by holes in semiconductors (gallium arsenide, aluminum gallium arsenide, indium gallium arsenide, indium phosphide, etc.) used for fabricating ordinary heterostructures. This is a phenomenon in which electrons having a smaller effective mass move from a conduction band having a small state density to a valence band having a large state density. For this reason, the tunnel probability is larger than in-band tunneling. Therefore, it is easy to reduce the tunnel current and the leakage current.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the tunneling field effect transistor according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an element according to the first aspect. P-type gallium antimonide (GaSb) layer 1 as a first semiconductor, intrinsic aluminum antimonide (AlSb) as a second semiconductor
Layer 2, intrinsic indium arsenide (InA) as the third semiconductor
s) Layer 3 is used . A. published by Morikita Publishing Co., Ltd. G. FIG. Mi
Runes & D. L. Original by Feucht, Yoshio Sakai Kiyoshi Takahashi Mori
Izumi Toyoei Co-translation “Semiconductor Heterojunction” Table 8 on page 8
As described in reference 1), AlSb, InAs
Have electron affinities of 3.65 eV and 4.9 eV, respectively.
It is. Therefore, the InAs charge as viewed from the electrons in the semiconductor
The electron affinity (conduction band energy) is the electron affinity of AlSb.
1.25 eV lower than the force (conduction band energy), Al
A two-dimensional charge is applied to the InAs side of the interface between the Sb layer 2 and the InAs layer 3.
A child gas 9 is formed. In the figure, a source electrode 8 and a drain electrode 5 are in ohmic contact with a two-dimensional electron gas 9 using thermal diffusion of an electrode material. FIG. 2 is an energy band diagram in the first structure. Described in Reference 1 above
As shown, the electron affinity of GaSb is 4.06e.
V, the band gap is 0.68 eV, and the energy of the valence band is
4.74 eV. Therefore, the valence band of GaSb
The energy of 4.74 eV is the electron affinity (transfer) of InAs.
From 4.9 eV, higher energy for electrons
On the rugie side . The states when the potential of the gate electrode 6 with respect to the p-GaSb layer 1 is changed from minus to plus are shown as (a), (b), and (c). The quantum level formed in the InAs layer 3 changes as shown in the figure by the application of the gate voltage, and becomes the same as the energy of the valence band of the P-type GaSb layer 1 in the state shown in FIG. At this time, inter-band tunneling occurs through the AlSb layer 2. When band-to-band tunneling occurs, the number of electrons in the quantum level increases, and at this time, the drain current increases.
Therefore, the gate electrodes shown in FIGS.
When changed as shown in (c), the drain current first increases as shown in FIG. 3 and then decreases. Therefore, the drain current changes with a differential negative resistance to the application of the gate voltage.

FIG. 4 shows a device according to claim 2 and FIG. 5 shows an energy band diagram thereof. The principle of operation is the same as that of the element of FIG. 1, but it operates in a complementary manner to the element of FIG.

[0008]

According to the tunneling field-effect transistor of the present invention, compared to the conventional in-band (in the conduction band or in the valence band) tunneling, the inter-band tunneling between the conduction band and the valence band is used. And a large tunnel current can be obtained. Therefore, the operating temperature range and the operating margin can be expanded.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a band diagram for explaining the operation of the embodiment of the present invention.

FIG. 3 is a diagram showing current-voltage characteristics of a device according to an example of the present invention.

FIG. 4 is a sectional view showing another embodiment of the present invention.

FIG. 5 is a band diagram for explaining the operation of another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 p-type GaSb layer 2 intrinsic AlSb layer 3 intrinsic InAs layer 4 drain electrode diffusion region 5 drain electrode 6 gate electrode 7 source electrode diffusion region 8 source electrode 9 two-dimensional electron gas 10 two-dimensional hole gas 11 n-type InAs layer 12 intrinsic GaSb layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Investigated field (Int.Cl. ⁶ , DB name) H01L 21/337-21/338 H01L 27/095-27/098 H01L 29/775-29/778 H01L 29 / 80-29/812

Claims (2)

(57) [Claims] A first semiconductor having p-type conduction characteristics;
Valence band energy with lower electron affinity than the first semiconductor
Ghee large second semiconductor, a first semiconductor valence conductive intrinsic
The third semiconductor has an electron affinity greater than the energy of the child band, and the second semiconductor is thin enough to allow a tunnel current to flow from the first semiconductor to the third semiconductor. A tunneling field-effect transistor having a source electrode, a gate electrode, and a drain electrode. 2. A first semiconductor having n-type conduction characteristics;
Valence band energy with lower electron affinity than the first semiconductor
A second semiconductor with high energy , an intrinsic third semiconductor having a valence band energy smaller than the electron affinity of the first semiconductor, and the second semiconductor tunnels from the first semiconductor to the third semiconductor. A tunneling field-effect transistor, which is thin enough to allow a current to flow and has a source electrode, a gate electrode, and a drain electrode on a third semiconductor.